If you're baffled by Nvidia's crazy naming scheme for video cards, this simple chart will help you determine where each falls in a hierarchy of graphics performance.
Anyone who's ever tried to buy an Nvidia card has undoubtedly been confused by the chipset names: you've got the 9500 GT which is somehow worse than a GTX 275, which is somehow better than a GTS 450 -- the numbers and letters just don't make much sense. Hidden away on Nvidia's website is this simple graph that compares each of their modern GPUs to one another with a simple benchmark value. Obviously there's a bit more to it than this -- certain cards are better at certain things and have different features -- but if you're trying to find out where your card falls in the hierarchy of Nvidia cards, this is a pretty simple way to see where it goes.
If you're an AMD fan, you can generally just look at the numbers on the cards (since the hierarchy is fairly well organized), and if you'd like to compare both companies against one another, or if you are comparing cards for actual shopping purposes, you can use something like Anandtech's GPU comparison tool.
The original graph is on the "Performance" page of every video card on geforce.com, so the link below is just one of the many pages on which it appears. Check out geforce.com for more info.